Method and apparatus for joining the electrodes of an electroslag remelting system

ABSTRACT

A method for joining the electrodes for electroslag remelting comprises arranging the electrodes in a feeding position in which they are fed downwardly one above the other relative to an ingot to be remelted and welding at least the core regions of the two electrodes together by subjecting them to currents of high intensity. An electrode feeding device comprises a vertical stand with first and second electrode holders on the stand which are independently vertically movable thereon. Each holder is insulated from the associated stand and from each other and from ground and it is provided with clamping means for clamping an electrode in a position in which its axis extends substantially vertically above the ingot to be remelted. During operation, the holders are moved vertically such that the electrode held by the uppermost holder is positioned into abutting contact with the top of the electrode held by the lowermost holder. The apparatus also advantageously includes a centering, packing and insulating ring which surrounds the space between the two abutting electrodes and which may advantageously be made with a funnel-shaped upper portion which may be filled with a slag.

Unite States Patent 91 Zimmermann et al.

[451 Aug. 14, 1973 METHOD AND APPARATUS FOR JOINING THE ELECTRODES OF ANELECTROSLAG REMELTING SYSTEM [75] Inventors: Erich Zlmmennann,

l-lattingen-Blankenstein; Nikolaus Forster, Dortmund-Brackel, both ofGermany [73] Assignee: Rheinstahl Huttenwerke AG, Essen,

Germany [22] Filed: Sept. 19, 1972 [21] Appl. No.: 290,371

[30] Foreign Application Priority Data Oct. 16,1971 Germany P 2151 617.6

[52] US. Cl. 13/18, 13/34, 219/69 E [51] Int. Cl. 1105b 7/10 [58] Fieldof Search 13/18, 9 ES, 14-17, 13/34; 219/69 E, 119, 120, 145, 146

[56] References Cited UNITED STATES PATENTS 2,845,293 7/1958 Peckham,Jr. 13/18 X 3,400,206 9/1968 Barth 219/145 X Primary Examiner-Roy N.Envall, Jr. Attorney-John .1. MeGlew et a1.

A method for joining the electrodes for electroslag remelting comprisesarranging the electrodes in a feeding position in which they are feddownwardly one above the other relative to an ingot to be remelted andwelding at least the core regions of the two electrodes together bysubjecting them to currents of high intensity. An electrode feedingdevice comprises a vertical stand with first and second electrodeholders on the stand which are independently vertically movable thereon.Each holder is insulated from the associated stand and from each otherand from ground and it is provided with clamping means for clamping anelectrode in a position in which its axis extends substantiallyvertically above the ingot to be remelted. During operation, the holdersare moved vertically such that the electrode held by the uppermostholder is positioned into abutting contact with the top of the electrodeheld by the lowermost holder. The apparatus also advantageously includesa centering, packing and insulating ring which surrounds the spacebetween the two abutting electrodes and which may advantageously be madewith a funnel-shaped upper portion which may be filled with a slag.

12 Claims, 3 Drawing Figures Patented Aug. 14, 1973 3,752,896

FIG] FIG-2 FIG-3 METHOD AND APPARATUS FOR JOINING THE ELECTRODES OF ANELECTROSLAG REMELTING SYSTEM BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates in general to a method and apparatusfor welding and, in particular, to a new and useful method for joiningthe electrodes for electroslag remelting when they are in a feedingposition during the remelting, and wherein the electrodes are weldedtogether, and to an improved apparatus therefor.

2. Description of the Prior Art The problem of changing electrodes inthe remelting of electroslags has not been solved satisfactorily as ofnow. In the usual method, the molten electrode is replaced as soon aspossible by a new one by means of feeding and holding devices for theelectrodes. With such devices, however, a temporary interruption duringthe remelting of the last electrode is unavoidable. In addition, theslag is cooled during the introduction of the new electrode and this canlead to changes in the structure of the ingot. In order to avoid this,the slag is heated during the change of the electrodes by the use of anadditional or auxiliary electrode, or the new electrode is preheated.

It is, of course, possible to use a single or very long electrode whichwill produce the entire ingot so that there will be an undisturbedmelting process. Generally speaking, however, the overall height whichis available will not permit this particularly for large ingots. Becausethe electrode generally has a smaller crosssection than the ingot, ithasalso been tried to connect one electrode during the melting with asecond electrode with a ring-shaped welding wire which is arranged atthe edge of the electrodes. In order to premade conical and the ends ofthe electrodes are provided with a corresponding conical recess and witha further recess to receive the marginal weld to be produced by theelectric welding. With this method, it is necessary to machine theelectrode ends prior to their use and it is difficult to handle theelectrodes because of the formation of the electric welds while theelectrode is in use, particularly since the electric welds must have asufficiently large cross-section so that they will not break open byheating which would cause the bottom electrode to fall off during thetransfer of current in the remelting of the electroslag.

SUMMARY OF THE INVENTION In accordance with the present invention, amethod and apparatus is provided, which insures that the usual -machinedelectrodes can be safely joined with each other without great costs andin a manner such that the joint will withstand the current load and theelectrode parts will not separate and fall into the sump of the remolteningot. With the present invention, this problem is solved in a method inwhich the two electrodes are joined for the remelting of the electroslagwhile they are in a feeding position and during the remelting and bywelding at least the core regions of the two elec-- trodes togetherusing current of high intensity. The welding of the core regions usinghigh current intensities yields a rapidly produced large surfaced jointbetween the two electrodes which can absorb the high current densitiesof the remelting process without undue heating, and which holds theelectrode safely to its end during the conical remelting of the rest ofthe bottom electrode because the electrodes are joined together in theircenters.

The welding of the two electrodes with high current densities iseffected best by pressing them against each other and by carrying out aflash-butt welding. The welding may also be carried out by means of anelectroslag remelting. ln both methods, the current available in thechill mold for the remelting of the electroslag can be used for joiningthe electrodes together. It is possible to work with an auxiliarycurrent source also.

When using electrodes having very large diameters, they are generallyprovided with a journal which is cast or forged on the end of the upperelectrode to keep the clamping device, which is necessary for supportingthe electrode, to much smaller dimensions than would normally berequired. Such end journals, which are tapered with regard to the restof the electrode diameter, are of particular advantage for the method ofthe invention because they ensure a very uniform welding due to thesmaller contact surface with the counter-electrode which is required.

An apparatus for the invention includes an electrode feeding devicewhich comprises a vertical support or stand which carries two verticallyspaced electrode holders wich can be moved upwardly and downwardlyrelative to the holder and relative to each other. Each holder includesmeans for clamping an electrode therein and the electrodes are insulatedfrom the other holder and from the ground and they are provided withquick opening and closing clamping means. The lower holder includesclamping means for engaging and clamping the operating electrode whichis introduced into the molten pool of the ingot or mold and the upperelectrode is held in position by the upper clamp or holder so that itmay be moved axially relative to the first electrode. By the provisionof the electrical insulation of the holders in respect to each other, itis possible to eliminate the welding current which is supplied from thecurrent source of the ESU plane by one electrode holder through theweld, and by the second electrode holder through the weld. It is alsopossible to supply the current over the upper electrode holder and toeliminate the current to the ingot which is to be remelted. The weld andthe point at which the remelting of the electrode slag takes place arethen connected in series.

The welding of the electrodes may be carried out in accordance withflash-butt welding techniques and, in such a case, it is advantageous tomake the support and the electrode holders and the drive for theelectrode holders very strong. The weight of the upper electrode helpsto produce the necessary contact welding pressure downwardly on the topof the lower electrode. Particularly with electrodes of largecross-sections, the start of the welding process can be accelerated bybriefly lifting the upper electrode after contact with the lowerelectrode in order to produce ,an electric are. It is advantageous toprovide the lower electrode with a centering, packing and insulatingdevice in the form of a ring which may advantageously have its upper endoutwardly flaring or funnel-shaped. This facilitates the centralattachment of the upper electrode to the bottom electrode and protectsthe holding device against liquid welding material and ensures that thewelded joint will remain warm when the two electrodes are weldedtogether.

When the electrodes are welded together by means of the electroslagremelting method, the device is provided with a short intermediate chillmold with the upper funnel-shaped portion and which includes a lowerportion of a diameter slightly larger than the diameter of theelectrode. The intermediate mold is electrically insulated on thesupport therefor and it can be moved vertically coaxially to theelectrodes. The welding of the two electrodes is effected by starting asecond electroslag remelting process in the intermediate mold in orderto form a melt sump and, after the formation of the melt sump, the upperelectrode is dipped into the sump in order to interrupt the melting andto start the welding. The two electrode slag remelting zones which areformed, one in the intermediate mold, and one in the main mold below thefirst electrodes, can be connected in series e'lectrically or they canbe operated electrically independently of each other. With this device,the two electrodes can be welded with each other over their entiresurfaces without pressure.

Accordingly, it is an object of the invention to provide an improvedmethod for joining the electrodes for electroslag remelting while theyare in a feeding posh tion for the electrodes and during the remeltingand wherein at least the core regions of the two electrodes are weldedtogether'by applying currents of high inten sity to the electrodes. I jv I i A further object of the invention is to provide a method ofjoining two electrodes together which corn prises arranging them in afeeding position on separate holders with their axes aligned and withone above'the other, directing theilowermost one into the ingot andapplying a current thereto in order to melt the ingot and,while thecurrent is still applied to the first ingot, lowering the seconduppermost ingot into abutting contact with the lowermost, and welding itto thelowermost ingot by lifting above the lowermost ingot to form anare or by forming a melt around the abutting first and secondin'gots'which may be advantageously filled with a slag and containedwithin a container located around the ingots between the abutting. areasthereof. n j I n A further object of the invention is to providean'apparatus for feeding electrodes which comprises a vertical standhavingfirst and second vertically movable electrode holdersthereon'which are adapted to be arranged over an ingot and which eachinclude clamping means for clamping a separate ingot with the upperholder being movable relative to the lowermost holder in order to abutthe upper electrodeagainstthe lower electrode and with each' holderbeing insulated from each other.

A further object of the invention to provide an ap-' paratus forsupporting electrodes for electroslag re-. melting and for joining theelectrodes together during the remelting process which is simple indesign, rugged in construction and economical to manufacture.

For an understanding of the principles of the invention, reference is'made to the following description of typical embodiments'thereof asillustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWI In the Drawings:

FIG. 1 is a side elevational view, partly in section, of an apparatusfor the feeding of electrodes in an electroslag melting process; 7

FIG. 2 is an elevational view of a combined electrode used forelectroslag remelting; and

FIG. 3 is a view similar to FIG. 1 of another embodiment of theinvention.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance withthe-method of the invention, two electrodes 1 and 2 are arranged in afeeding position in which they feed into a slag pool formed at the topof an ingot mold 9. In the inventive method, the core regions of the twoelectrodes are welded together at the abutting contact point between thetop of the lowermost electrode 1 and the bottom of the uppermostelectrode 2. The invention includes an apparatus for feeding theelectrodes 1 and 2 vertically which includes a vertical stand 4, havingtwo electrode holders 5 and 6, which are relatively movable thereonupwardly and downwardly independently. In the preferred arrangement, theelectrode holders 5 and 6 may be moved independently relative to eachother in a vertical direction over the full height of the stand 4. Thetwo electrode holders 5 and'6 are insulated against each other andagainst the ground. They include quick closing clamping arms or clampingmeans 7 and 8, respectively.

When the melting process is started, the electrode 1, which is clampedat the lower electrode holder 5, is moved with the holder 5 downwardlytoward the ingot mold 9. The electrode isclamped so that the top edgeranged at its topmost position. Shortly before the electrode holder 5reaches itsbottom position, the .electrode 2 is lowered sufficientlytocause the electrode to engage against the top of the electrode 1 Theelectrical current circuit. to the electrode 1 and to ingot mold 9 isinterrupted and the current source is applied to the electrodes 1 and 2with a sufficiently high potential to cause the starting of a weldingprocess between the two electrodes. The bottom end of the electrode 2 isslightly recessed so that the welding of the core region of theelectrode of at least one fifth of the electrode diameter is ensured.Then the welding circuit is opened and the electrode 1 is connected tocontinue the remelting operation. After an adequate cooling of the jointweld, the

clamping means 7 carried by the lower holder 5 is opened and theelectrode holders is moved up to the electrode holder 6 and the clampingmeans 7 thereon is closed around the newly positioned'electrode 2. Aclamping means 8 of the upper electrode holder 6 is openedandtheelectrode is advanced by the electrode holder 5 to continue the meltingoperation.

In order to be able to join the two electrodes 1 and 2 better beforethey are welded, and also to prevent overlfowing of the welding materialfrom damaging the clamping means 7 beneath the joints between theelectrodes l and '2 when they are welded together, the inventionprovides a protection device in the form of a funnel-shaped insulatedcentering, packing and insulating device 10. The device 10 is in theform of a ring which extends around the electrodes 1 and 2 and isadvantageously positioned to encompass the joint therebetween.

In FIG. 2 there is indicated an electrode of a very large diameter,generally designated 20, and which includes a lower or first electrodeportion 1 and an upper or second electrode portion 2' which areinterconnected by a clamping journal 11 which has a smaller diameterthan the electrodes in order to facilitate its being placed in theclamping devices 5 and 6. In addition, a further top journal 12 isprovided at the upper end of the second electrode 2' in order to permitit to be clamped by the clamping device 6. When such electrodes are usedin the electrode feeding devices, according to the arrangement shown inFIG. 1, the clamping journals 11 and 12 of the electrode 20 have alength which is at least equal to the distance of the bottom edge of theclamping means 7 from the upper edge of the clamping means 7 at thegreatest approach of the two electrode holders 5 and 6. This isnecessary so that the electrode can be transferred from one clampingmeans to the other.

In the embodiment shown in FIG. 3, the apparatus includes the samedevices shown in FIG. 1 but also includes an intermediate mold 13 whichis carried on a holder 16 which is also movable on the stand 4. Theintermediate mold 13 includes an upper funnel-shaped part 14 and a lowerpart 15 having'an inside diameter ,which is substantially the same asthe diameter of the electrodes 1 and 2.

With the apparatus of FIG. 3, the welding of the two electrodes 1 and 2is effected as follows:

When the electrode 1 melts down, it is pulled by the descendingelectrode holder 5 through the mold 13 while the mold 13 is being moveddownwardly but at a slower rate. When the end of the electrode 1 hasarrived in the funnel-shaped portion 14 of the mold 13, the electrodeholder 5 and the mold holder 16 are moved downwardly at the same speed.The funnelshaped part 14 of the mold 13 is filled with a slag 17 and theelectrode 2 is lowered by means of the electrode holder 6 until it comesinto contact with the electrode 1. The current which is supplied isswitched from the clamping means 7 for flow throughthe electrode 1 tothe clamping means 8 for flow through the electrode 2. Then theelectrode 2 is lifted slightly away from the electrode 1 and the voltageis increased in order to draw an arc. In this way, the electroslagremelting process is started in the intermediate mold 13. The twoelectroslag remelting zones in the intermediate mold 13 and in the ingotmold 9 are then connected in series. The voltage is increased and, afterliquefaction of the slag 17, the movement of the mold holder 16 is'stopped. Care must be taken during the remelting of the electrode 2 inthe intermediate mold 13 to ensure that the liquid metal parts arecontained only in the lower part 15 of the mold 13 in order to preventany break-offs of the material.

After the formation of melt sump in the lower part 15 of theintermediate mold 113, the upper electrode is moved downwardly throughthe slag until it dips into the melt sump. The melting process of theelectrode 2 is thus interrupted and the two electrodes 1 and 2 arewelded together. During the uniform lowering of the electrode holders 5and 6, the weld issues at the bottom from the mold 13. Then, afterloosening of the clamping means 7, mold 13 and electrode holder 5 aremoved upwardly and the clamping means 7 is closed. The current supply isswitched from the clamping means 8 to the clamping means 7 and theclamping means 8 are loosened. In order to accelerate thesolidification, the current supply can also be switched from clampingmeans 8 to the clamping means 7 at the end of the melting process so asto not stress the solidifying weld by the current for the electroslagremelting process in the mold.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. A method for joining the electrodes which are fed into associationwith an ingot within an ingot mold comprising arranging a first andsecond electrode in a feeding position on which they extendsubstantially vertically above the ingot, feeding the lowermostelectrode into engagement with the ingot in order to cause the meltingthereof and welding the second uppermost electrode to the firstelectrode under high current intensity in order to joint together thetwo electrodes at least in the core regions.

2. A method according to claim 1, wherein the electrodes are welded withhigh current intensities by pressing them against each other to effect aflash-butt welding..

' 3. A method according to claim 1, wherein the two electrodes arewelded together by means of electroslag remelting.

4. A method according to claim 1, wherein one of the electrodes has anend journal which is tapered with respect to the rest of the electrodediameter.

5. A method of electroslag remelting using a series of electrodes whichare introduced into engagement with an ingot in an ingot mold comprisingenergizing a first electrode in order to cause it to melt the ingot andto be consumed into the melt of the ingot as it is moved toward theingot, arranging a second electrode in axial 1 alignment behind thefirst electrode and advancing it into contact with the first electrodeand welding the second electrode to the first electrode as the firstelectrode is being consumed in the melt bath.

6. A method of electroslag remelting, according to claim 5, includingputting a centering, packing and insulation means around the top end ofthe first electrode and a portion of the bottom end of the secondelectrode after it is in abutting engagement with the first electrodeand maintaining the insulation means in position when the firstelectrode is welded to the second electrode.

7. A method of electroslag remelting, according to claim 6, wherein theinsulation includes a small diameter portion and an upper outwardlyflaring funnel portion and including applying a slag material into thefunnel portion after initiating the welding.

8. A method of electroslag remelting, according to claim 5, whereinafter the first electrode has been consumed to a predetermined amountand the second electrode is moved downwardly to engage its lower endagainst the top of the first electrode, the current supplied to thefirst electrode and the ingot is discontinued and it is applied insteadto the first and second electrodes to start a welding processtherebetween, and wherein the second electrode is moved upwardly off thefirst electrode to effect a flash-welding.

9. An electrode feeding device, comprising a vertical stand, a firstelectrode holder on said stand movable upwardly and downwardly thereon,a second electrode holder on said stand located over said firstelectrode holder and being movable upwardly and downwardly thereon,insulating means insulating each holder against said stand and againstthe ground, said first holder having a first clamping means for clampingan electrode in a position with its axis extending substantiallyvertically and above the ingot mold, said second electrode holder havingsecond clamping means for holding a second electrode in a position withits axis substantially vertical and above the electrode carried by saidfirst holder, said first and second holders being movable relative toeach other to effect abutment of the upper electrode of the secondelectrode holder against the top of the lower electrode carried by thefirst electrode holder.

10. An electrode feeding device, according to claim 9, including a ringarranged around said first and second electrodes in the area of theirabutting contact.

11. An electrode feeding device, according to claim 10, wherein saidring is made of an insulating material and it includes a lower portionextending around the lowermost electrode and an upper outwardly flaringfunnel-shaped portion for receiving a slag.

12. An electrode feeding device, according to claim 9, wherein saidfirst electrode includes first and second vertically spaced widediameter portions with an intermediate portion of smaller diametertherebetween and including an upper portion of smaller diameter thansaid first and second portions, said intermediate and said upperportions comprising journal portions for engagement with said first andsecond holders, respectively, said upper smaller diameter portion beingtwice the length of said intennediate smaller diameter portion.

1. A method for joining the electrodes which are fed into associationwith an ingot within an ingot mold comprising arranging a first andsecond electrode in a feeding position on which they extendsubstantially vertically above the ingot, feeding the lowermostelectrode into engagement with the ingot in order to cause the meltingthereof and welding the second uppermost electrode to the firstelectrode under high current intensity in order to joint together thetwo electrodes at least in the core regions.
 2. A method according toclaim 1, wherein the electrodes are welded with high current intensitiesby pressing them against each other to effect a flash-butt welding.
 3. Amethod according to claim 1, wherein the two electrodes are weldedtogether by means of electroslag remelting.
 4. A method according toclaim 1, wherein one of the electrodes has an end journal which istapered with respect to the rest of the electrode diameter.
 5. A methodof electroslag remelting using a series of electrodes which areintroduced into engagement with an ingot in an ingot mold comprisingenergizing a first electrode in order to cause it to melt the ingot andto be consumed into the melt of the ingot as it is moved toward theingot, arranging a second electrode in axial alignment behind the firstelectrode and advancing it into contact with the first electrode andwelding the second electrode to the first electrode as the firstelectrode is being consumed in the melt bath.
 6. A method of electroslagremelting, according to claim 5, including putting a centering, packingand insulation means around the top end of the first electrode and aportion of the bottom end of the second electrode after it is inabutting engagement with the first electrode and maintaining theinsulation means in position when the first electrode is welded to thesecond electrode.
 7. A method of electroslag remelting, according toclaim 6, wherein the insulation includes a small diameter portion and anupper outwardly flaring funnel portion and including applying a slagmaterial into the funnel portion after initiating the welding.
 8. Amethod of electroslag remelting, according to claim 5, wherein after thefirst electrode has been consumed to a predetermined amount and thesecond electrode is moved downwardly to engage its lower end against thetop of the first electrode, the current supplied to the first electrodeand the ingot is discontinued and it is applied instead to the first andsecond electrodes to start a welding process therebetween, and whereinthe second electrode is moved upwardly off the first electrode to effecta flash-welding.
 9. An electrode feeding device, comprising a verticalstand, a first electrode holder on said stand movable upwardly anddownwardly thereon, a second electrode holder on said stand located oversaid first electrode holder and being movable upwardly and downwardlythereon, insulating means insulating each holder against said stand andagainst the ground, said first holder having a first clamping means forclamping an electrode in a position with its axis extendingsubstantially vertically and above the ingot mold, said second electrodeholder having second clamping means for holding a second electrode in aposition with its axis substantially vertical and above the electrodecarried by said first holder, said first and second holders beingmovable relative to each other to effect abutment of the upper electrodeof the second electrode holder against the top of the lower electrodecarried by the first electrode holder.
 10. An electrode feeding device,according to claim 9, including a ring arranged around said first andsecond electrodes in the area of their abutting contact.
 11. Anelectrode feeding device, according to claim 10, wherein said ring ismade of an insulating material and it includes a lower portion extendingaround the lowermost electrode and an upper outwardly flaringfunnel-shaped portion for receiving a slag.
 12. An electrode feedingdevice, according to claim 9, wherein said first electrode includesfirst and second vertically spaced wide diameter portions with anintermediate portion of smaller diameter therebetween and including anupper portion of smaller diameter than said first and second portions,said intermediate and said upper portions comprising journal portionsfor engagement with said first and second holders, respectively, saidupper smaller diameter portion being twice the length of saidintermedIate smaller diameter portion.